The present invention relates to a multiline subscriber telephone system, and a method of operating such a system, which implements an incoming call-waiting feature for an incoming call on an external telephone line which is in use on a conference call without requiring that the conference call be suspended while the incoming call is answered.
FIG. 1 is a block diagram of a subscriber telephone system. In FIG. 1, a plurality of bidirectional external telephone lines 5 are coupled to corresponding terminals of a telephone system termed customer premises equipment (CPE) 30. The CPE 30 is also bidirectionally coupled to a plurality of handsets 20. The handsets 20 may be coupled to the CPE 30 via standard phone wires, or via wireless radio transceivers in the CPE 30 and the handsets 20, or via a combination of wired and wireless links.
For example, current multiline business phone systems can link up to four external telephone lines to up to twelve corresponding handsets. These handsets may be, for example, wireless handsets operating over a radio frequency (RF) link in the 900 MHz unlicensed frequency band. In general, when a user wishes to place an outgoing call, he picks up one of the handsets 20. The CPE 30 senses this, and connects that handset to an unused one of the external phone lines 5. The user hears a dial tone and makes the outgoing call in the usual manner. When an incoming call arrives on one of the external phone lines 5, the CPE 30 assigns one of the handsets 20 to that phone line.
There are many known techniques for assigning the incoming phone call to a handset. For example, the assignment may be a permanent assignment in which each handset 20 is assigned to a corresponding one of the external telephone lines 5, or the CPE 30 may simply route the incoming call to any unused handset 20, or all incoming calls may initially be routed to a single handset 20 (e.g. a receptionist), or all of the handsets 20 may ring in response to all incoming calls. Any technique for assigning the incoming call to one or more handsets may be used. The handset 20 assigned to receive the incoming phone call rings, the user picks up the handset 20 and responds to the incoming call in the usual manner.
There are several known features which may be provided by a telephone system 10 such as is illustrated in FIG. 1. For example, the system 10 can provide internal users of the system with an intercom feature. This feature may be implemented by allowing one internal user to call another directly through the CPE 30 without using any of the external telephone lines 5. This feature may also allow several internal users to form an internal conference call amongst themselves, also through the CPE 30 without using an external telephone line 5, all in a known manner.
Another example is the ability to form a conference call by allowing more than one of the handsets 20 to be connected to a single external telephone line 5, thus enabling more than one local user to talk to the party at the other end of the external telephone line 5. This feature may be implemented by allowing a user to place an outgoing call over one of the external telephone lines 5 in the manner described above, and then allowing the user to attach other internal users to that telephone call by connecting their handsets 20 in common to the external telephone line 5 connected to the outside party, all in a known manner.
A known feature, which is provided by the telephone transmission system to which the external telephone lines 5 are coupled, is xe2x80x9ccall waitingxe2x80x9d. This feature provides an alert signal to a subscriber handset which is currently engaged in a telephone call when an incoming call is attempting to connect to that subscriber""s handset. In response to the alert signal, the handset provides an indication of an incoming phone call to the subscriber, in the form a beep. In response to this indication, that subscriber may temporarily suspend the current telephone call (i.e. put it on xe2x80x9choldxe2x80x9d) and answer the incoming telephone call. When the newly received telephone call is complete, the subscriber may reconnect to the original telephone call.
In a normal consumer arrangement where a standard telephone is attached to the external telephone line, no special circuitry or equipment is necessary to implement this feature, because this feature is provided by the central office. In a multiline subscriber telephone system in which a plurality of handsets 20 are connected to a plurality of external telephone lines 5, the CPE 30 need not provide any services for this feature other than connecting a handset 20 to an external telephone line 5. However, because the multiline telephone system may also provide other functions in conjunction with the xe2x80x98call waitingxe2x80x99 feature, and/or enhancements to the xe2x80x98call waitingxe2x80x99 feature, the CPE 30 in such a system may include circuitry to interact with the central office, and provide the xe2x80x98call waitingxe2x80x99 feature.
Another known feature which is provided by the telephone transmission system is xe2x80x9ccaller identification (ID)xe2x80x9d. This feature is implemented by the central office. xe2x80x98Caller IDxe2x80x99 inserts information about an incoming telephone call to a subscriber when the subscriber""s handset receives the indication of an incoming call. The information about the incoming telephone call includes the telephone number from which that call is made. That information may be displayed at the called handset 20, and used to determine who is calling and what action to take. This information may also be supplied to a computer system, which can look up previously stored data related to the calling telephone number and display that data to the called party.
There are two modes of xe2x80x98caller IDxe2x80x99. In mode I xe2x80x98caller IDxe2x80x99, the telephone being called is available to receive incoming telephone calls (i.e. on-hook). Information about the incoming phone call is transmitted from the central office to the handset being called as a part of the ring signal between the first and second rings. There must be apparatus at the location of the called handset which is capable of extracting this information and either displaying it, or supplying it to a computer system, as described above. The user of the called handset can consult the information displayed, or from the computer system, and decide whether to accept the incoming call and pick up the handset, or not.
Mode II xe2x80x98caller IDxe2x80x99 may be used in conjunction with the xe2x80x98call waitingxe2x80x99 feature described above. In mode II xe2x80x98caller IDxe2x80x99, the telephone being called may be engaged in a telephone call (i.e. off-hook). Information about the incoming call, including the calling telephone number, is sent along with the alerting signal which indicates that an incoming call is attempting to connect to the currently busy handset. As with mode I xe2x80x98caller IDxe2x80x99, there must be apparatus which can extract this information, and either display it, or supply it to a computer system. The subscriber receives the xe2x80x98call waitingxe2x80x99 beep, as described above, and can view the information relating to the incoming telephone call. Based on that information, the subscriber can decide whether to suspend the present telephone call and accept the new incoming call, or not.
One combination of the above known features is conference calling and xe2x80x98call waitingxe2x80x99. Referring again to FIG. 1, more than one local handset 20 can be simultaneously talking to an external party via one of then external telephone lines 5 when an incoming call arrives for that external telephone line. In currently known systems, when the CPE alerting signal (CAS) arrives from the central office, one, several, or all of the local handsets 20 produces a beep indicating that a call is waiting. In response, one of the handsets may take control and put the current conference call on hold to answer the incoming call. The controlling handset is connected, over the external telephone line, to the caller of the incoming call. This, however, puts the entire conference call on hold. None of the local handsets can talk to the original external conference party. Only when the controlling local handset 20 completes the telephone call to the newly arrived incoming call is the external party reconnected to the local handsets 20 and the conference call reestablished.
It is desirable that the users of local handsets 20 involved in a conference call be notified of a newly arrived incoming call. However, it is also desirable that the user of the controlling one of the local handsets 20 be able to answer the incoming call without unduly interrupting the conference call.
In accordance with principles of the present invention, a method for responding to an incoming call on one of a plurality of external telephone lines when a conference call is in progress on that external telephone line includes the following steps. First, mode II caller ID information is received relating to the incoming call. Then the plurality of handsets involved in the conference call are notified that an incoming call has been received. Should it be desired to answer that incoming telephone call, a pre-recorded message is transmitted to the caller of the incoming call requesting the caller hang up. The caller of the incoming call is then called back on a unused external telephone line using the previously received caller identification information relating to that incoming call. Finally, one of the plurality of handsets involved in the conference call is connected to the caller of the incoming call.
In accordance with another aspect of the present invention, a subscriber telephone system includes a source of a plurality of external telephone lines, a plurality of handsets, and a base unit which is coupled between the external telephone line source and the handsets. There is conference call circuitry in the base unit which establishes a conference call involving the handsets and one of the external lines. Caller identification circuitry, which is coupled to the external telephone lines, receives caller identification information related to an incoming telephone call on the conference call line. Call waiting circuitry sends a notification to the handsets that an incoming call has been received, and receives instructions from a controlling handset to respond to the incoming call by callback. Voice message circuitry transmits a pre-recorded message to the caller of the incoming call requesting the caller hang up. Callback circuitry places a callback to the caller of the incoming call on an unused line using the caller identification information, and connects the controlling handset to the callback line.
A multiline subscriber telephone system according to the present invention provides the call-waiting function for an external telephone line carrying a conference call without requiring that the conference call be unduly interrupted, and without requiring any changes to the central office.